#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  string S; cin >> S;
  int ans = 0;
  for(int i = 0; i < (int)S.size(); i++){
    int s = S[i]-'0';
    ans += s;
  }
  cout << ans << endl;
}